The invention relates to a gripper mechanism for devices for handling objects in the form of sheets or plates, in particular for post processing machines.
Generally known gripper mechanisms of this type, which have been in use for a long time, contain a gripper arm which can pivot about a gripper arm pivoting shaft, which gripper arm can be moved transversely with respect to the movement direction of a transfer chain, which is driven intermittently for example, by means of an appropriate drive, for example a crank drive, to carry out reciprocating pivoting movements. At its free end, the gripper arm is fitted with a gripper hand which has a pair of interacting gripper claws of which, in general, one is designed to be fixed relative to the gripper arm and the other is fitted such that it can pivot relative to the gripper arm. The pivoting gripper claw is moved by means of a claw operating drive against the force of spring means, which hold the gripper claws in the closed position, in specific pivoting positions of the gripper arm to the open position in order to grip either a specific object in the form of a sheet or plate, or a corresponding stack of such objects, and once the gripper claws have closed, to transport them to the transfer chain or else, when this handling process has been completed, to release the relevant object or stack of objects once again so that the compartment on the transfer chain which has now been filled can continue to move with said chain. One known embodiment of a gripper claw operating drive provides an operating lever arrangement which is mounted on the gripper arm such that it can pivot, can be pivoted by means of a claw operating drive apparatus during the pivoting movements of the relevant gripper arm, and is connected via a coupling linkage to the gripper claw which can pivot with play or a clearance which allows a specific opening of the gripper claws against the force of the spring prestressing means regardless of the respective position of the operating lever arrangement. In general, the operating lever arrangements for a plurality of gripper arms which are operated at the same time and are forced to move synchronously in a reciprocating manner are seated on a common operating shaft which is mounted on each of the simultaneously moved gripper arms, and is rotated in a reciprocating manner in specific gripper arm pivoting positions via a slotted guide link, a slotted guide link feeler and a feeler roll lever, which is firmly attached to the operating shaft, in order to operate the respective pivoting gripper claws on the individual gripper arms simultaneously, so that the operating lever arrangements which are seated on the operating shaft move the moving gripper claws to the open position via the individual coupling linkage.
When a post processing machine is being prepared for a specific operating sequence, the gripper claws in the individual workstations are thus set to the thickness of the object to be handled or to the thickness of the stack of objects to be handled. In this case, the gripper claws associated with a gripper arm have to be moved by hand to the open position at the individual workstations. Since the prestressing means or spring means which force the gripper claw pairs into their closed position now exert considerable mechanical forces in order to allow the objects to be handled to be gripped and fixed securely, an operator faces difficulties, when preparing the machine for an operation or when setting and servicing the machine, into applying sufficient forces by hand at any point in the gripper claw operating drive or the gripper claw operating mechanism in order to overcome the force of the prestressing means. If a forceful attempt is made, parts of the post processing machine may be damaged. In particular, however, there is a risk of injuries and, furthermore, problems with manual operation become particularly difficult when the gripper claw operating drives for a series of gripper claw pairs are coupled via a common operating shaft which covers a plurality of workstations, so that the prestressing means provided on a relatively large number of gripper arms have to be overcome jointly in order to open one entirely specific gripper claw or one specific gripper claw pair.
The invention is intended to achieve the object of refining a gripper mechanism having the features of the precharacterizing clause of the attached Claim 1 so as to provide a simple capability, which reduces the risk of injury, for manual operation of the gripper claw pair or of a gripper arm. This object is achieved according to the invention by the features specified in the characterizing part of Claim 1. Advantageous refinements and developments of the gripper mechanism specified here also form the subject-matter of the patent claims which are dependent on Claim 1 and whose content is in consequence expressly made part of the description without having to repeat the wording at this point.
It is self-evident that the design of a gripper mechanism as specified here also achieves the aim, by means of a single component which has a very simple design and is cheap, particularly if it is made of plastic, not only of achieving the object described above but of improving the smooth running and wear resistance of such a gripper mechanism, since the manual operating part specified here also acts as a bearing component. It is also particularly advantageous that, in a gripper mechanism of the type specified here, the gripper claws on a specific gripper arm of a post processing machine can be opened by means of the respective manual operating element without the gripper claws on adjacent gripper arms also being opened and without having to overcome the prestressing force of more than only the prestressing means which are associated with just the relevant one gripper arm. A number of embodiments will be explained in more detail in the following text with reference to the drawings, in which: